test(photon): replace source-grep URL-routing tests with behavior tests

Follow-up to the URL markdown fix: extract the /send builder decision into
sidecar/send-format.mjs and rewrite test_url_send_path.py to execute the real
module under node (format+text in -> chosen builder out) instead of regex-
grepping index.mjs source, which is a banned test pattern in this repo.

plugins/platforms/photon/sidecar/index.mjs

@@ -66,6 +66,7 @@ import http from "node:http";
 import crypto from "node:crypto";
 import { once } from "node:events";
 import { patchSpectrumTs } from "./patch-spectrum-mixed-attachments.mjs";
+import { chooseSendFormat } from "./send-format.mjs";
 
 const projectId = process.env.PHOTON_PROJECT_ID;
 const projectSecret = process.env.PHOTON_PROJECT_SECRET;
@@ -894,10 +895,10 @@ const server = http.createServer(async (req, res) => {
       // iMessage API, which can 500 on messages containing raw URLs.
       // Plain-text URLs are auto-linked by iMessage, so route markdown
       // messages that contain URLs through spectrumText while preserving
-      // spectrumMarkdown for URL-free markdown.
-      const hasUrl = /https?:\/\/[^\s)'"<>]+/i.test(text);
+      // spectrumMarkdown for URL-free markdown. The decision lives in
+      // send-format.mjs so tests can exercise it directly.
       const builder =
-        format === "markdown" && !hasUrl
+        chooseSendFormat(format, text) === "markdown"
           ? spectrumMarkdown(text)
           : spectrumText(text);
       const result = await space.send(builder);

plugins/platforms/photon/sidecar/send-format.mjs

@@ -0,0 +1,27 @@
+// Outbound /send builder selection for the Photon sidecar.
+//
+// spectrumMarkdown() enables data detection (enableDataDetection) in the
+// underlying iMessage API, which can 500 on messages containing raw URLs.
+// Plain-text URLs are auto-linked by iMessage anyway, so markdown messages
+// that contain a URL are routed through the text builder, while URL-free
+// markdown keeps native markdown rendering.
+//
+// This lives in its own module (rather than inline in index.mjs) so tests can
+// execute the real decision logic under node instead of grepping source —
+// see tests/plugins/platforms/photon/test_url_send_path.py.
+
+const URL_RE = /https?:\/\/[^\s)'"<>]+/i;
+
+/**
+ * Decide which spectrum-ts builder the /send handler should use.
+ *
+ * @param {string} format "markdown" | "text" (already validated by /send)
+ * @param {string} text   the outbound message body
+ * @returns {"markdown"|"text"}
+ */
+export function chooseSendFormat(format, text) {
+  if (format === "markdown" && !URL_RE.test(String(text))) {
+    return "markdown";
+  }
+  return "text";
+}

tests/plugins/platforms/photon/test_url_send_path.py

@@ -1,50 +1,87 @@
-"""Regression tests for Photon raw-URL message delivery.
+"""Behavior tests for Photon raw-URL outbound routing (issue: markdown 500s).
 
 The iMessage markdown builder enables data detection inside spectrum-ts. On
 some IMAgentKit sends, that path returns a 500 when the message contains a raw
-URL. The sidecar should keep markdown rendering for URL-free messages, but use
+URL. The sidecar keeps markdown rendering for URL-free messages, but must use
 plain text for messages containing URLs so iMessage can auto-link them without
 hitting the data-detection failure path.
-"""
 
+The routing decision lives in
+``plugins/platforms/photon/sidecar/send-format.mjs`` (imported by index.mjs's
+``/send`` handler). These tests *execute* that real module under node and
+assert the chosen builder for representative payloads — they do not read the
+sidecar source.
+"""
 from __future__ import annotations
 
-import re
+import json
+import subprocess
 from pathlib import Path
+from typing import Dict, Tuple
+
+import pytest
+
+_MODULE = Path("plugins/platforms/photon/sidecar/send-format.mjs").resolve()
+
+_CASES: Dict[str, Tuple[str, str, str]] = {
+    # name: (format, text, expected builder)
+    "markdown_without_url_keeps_markdown": (
+        "markdown", "**bold** and `code`", "markdown",
+    ),
+    "markdown_with_https_url_falls_back_to_text": (
+        "markdown", "see **this**: https://example.com/a?b=1", "text",
+    ),
+    "markdown_with_http_url_falls_back_to_text": (
+        "markdown", "http://example.com", "text",
+    ),
+    "markdown_link_syntax_also_falls_back_to_text": (
+        "markdown", "[docs](https://example.com/docs)", "text",
+    ),
+    "markdown_with_uppercase_scheme_falls_back_to_text": (
+        "markdown", "HTTPS://EXAMPLE.COM is loud", "text",
+    ),
+    "markdown_bare_domain_without_scheme_keeps_markdown": (
+        # Only scheme'd URLs trip iMessage's data-detection 500; a bare domain
+        # is ordinary text and must keep markdown rendering.
+        "markdown", "ask example.com about *this*", "markdown",
+    ),
+    "text_format_stays_text": ("text", "plain message", "text"),
+    "text_format_with_url_stays_text": (
+        "text", "https://example.com", "text",
+    ),
+}
 
 
-SIDECAR = Path("plugins/platforms/photon/sidecar/index.mjs")
-
-
-def _source() -> str:
-    return SIDECAR.read_text(encoding="utf-8")
-
-
-def test_photon_sidecar_detects_raw_urls_before_builder_selection() -> None:
-    src = _source()
-
-    assert "hasUrl" in src
-    assert "https?:\\/\\/" in src
-    assert re.search(r"const\s+hasUrl\s*=\s*/https\?:", src)
-
-
-def test_markdown_builder_is_used_only_for_url_free_markdown() -> None:
-    src = _source()
-
-    assert re.search(
-        r'format\s*===\s*["\']markdown["\']\s*&&\s*!hasUrl',
-        src,
+@pytest.fixture(scope="module")
+def verdicts() -> Dict[str, str]:
+    """Run every case through the real send-format module in one node call."""
+    harness = (
+        f"import {{ chooseSendFormat }} from {json.dumps(_MODULE.as_uri())};\n"
+        "const chunks = [];\n"
+        "process.stdin.on('data', (c) => chunks.push(c));\n"
+        "process.stdin.on('end', () => {\n"
+        "  const cases = JSON.parse(Buffer.concat(chunks).toString('utf-8'));\n"
+        "  const out = {};\n"
+        "  for (const [name, [format, text]] of Object.entries(cases)) {\n"
+        "    out[name] = chooseSendFormat(format, text);\n"
+        "  }\n"
+        "  process.stdout.write(JSON.stringify(out));\n"
+        "});\n"
     )
-    assert "spectrumMarkdown(text)" in src
-
-
-def test_text_builder_is_fallback_for_markdown_messages_with_urls() -> None:
-    src = _source()
-
-    # Builder selection must still have spectrumText as the fallback branch so
-    # markdown+URL messages avoid spectrumMarkdown's data-detection path.
-    assert "spectrumText(text)" in src
-    assert re.search(
-        r'format\s*===\s*["\']markdown["\']\s*&&\s*!hasUrl[\s\S]*\?[\s\S]*spectrumMarkdown\(text\)[\s\S]*:[\s\S]*spectrumText\(text\)',
-        src,
+    payload = {name: [fmt, text] for name, (fmt, text, _) in _CASES.items()}
+    run = subprocess.run(
+        ["node", "--input-type=module", "-e", harness],
+        input=json.dumps(payload),
+        cwd=Path.cwd(),
+        text=True,
+        capture_output=True,
+        check=False,
     )
+    assert run.returncode == 0, run.stderr
+    return json.loads(run.stdout)
+
+
+@pytest.mark.parametrize("name", sorted(_CASES))
+def test_send_builder_selection(name: str, verdicts: Dict[str, str]) -> None:
+    _, _, expected = _CASES[name]
+    assert verdicts[name] == expected